[foxthreefour]

In an earlier thread I stated that I was having trouble with the ratios of a reaction that included a ketone and Copper (ii)Bromide reflexed in ETAC. The reaction mixture was becoming dark, with sludge being produced, not the deep green to amber that it should be.

Now forgive the naive nature of the question but, would the fact this is being carried out in a stainless steel reactor have anything to do with it? I ask because it has occurred to me I don’t know the grade of stainless used, and HBr is produced in the reaction which I assume could react with metals along with the ETAC.

Thanks in advance.

[Enthalpy]

Answering from the mechanical design world
https://media.distributordatasolutions.com/ThomasAndBetts/v2/part2/files/File_3227_emAlbumalbumstc_ustc_1_g_304sschartpdfClickHerea.pdf
HBr in 20% concentration has "severe effect" on 304 stainless steel. That's the most banal 18Cr-8Ni austenitic stainless steel.
https://www.industrialspec.com/images/files/316l-stainless-steel-chemical-compatibility-from-ism.pdf
same for the better 316L alloy, 18Cr-12Ni-Mo for marine applications.

This is from the consequences observed at the metal. The liquid uses to show colours and dirt well before the surface degrades.

Would CuBr₂ be already as corrosive as HBr? At least HCl corrodes stainless steel by its Cl^-, not by the more benign H⁺.

This holds for aqueous solutions, not EtAc which is known only from the chemical world.

[clarkstill]

The by-product of the reaction is HBr (see https://pubs.acs.org/doi/pdf/10.1021/jo01035a003). I don't know much about the engineering/materials aspects, but if your steel is vulnerable to HBr then I don't think you can use this method. Do you have other reactors available to you (e.g. glass, PTFE, hastelloy steel)?

[wildfyr]

Yes, I would say it is a bad idea to do a copper catalyzed reaction in steel. Also, halide ions tend not to agree with steel. Glass is the typical container, at least until the kinks are worked out for a given reaction.

I am also continually surprised by the influence of catalytic light whenever halogens are involved in a reaction.

[foxthreefour]

The same reaction has now been carried out in a vessel made from HDPE, with a much better result. No darkening and correct colours.

If the HBr is reacting with the steel, what could be being produced? FeBr?

[Enthalpy]

In aqueous conditions, Cl^- (and possibly Br^-) is said to spoil the CrO₂ protective layer on stainless steel, so usual corrosion by water (and air) occurs, not just by the halogen.

In you EtAc, I can't tell.